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Hong KongReshore contact and concrete load transfer
A reshore must be placed and adjusted according to the formwork design so it provides the intended support without jacking the slab or creating unplanned loads.
More key points
- OSHA requires firm contact at shore bearing points and requires reshores when partially cured concrete must carry loads beyond its capacity.
- The drawings and competent design control the installation.
On this page5 sections
A reshore can look like a simple post under a slab. Its job is structural: transfer construction loads through partially cured concrete while the original formwork and shores are removed or reused. The question “how tight?” is really a question about contact, load path, and the approved reshoring sequence. Start with the drawings.
| Field condition | What the crew should verify |
|---|---|
| Plan available | Current formwork and reshoring drawings, including revisions, are available at the jobsite. |
| Bearing points | Sills are sound and rigid; base plates, shore heads, extension devices, and adjustment screws make firm contact with the foundation and form. |
| Load path | The shore stands where the design intends and bears on a surface capable of carrying the transferred load. |
| Equipment condition | Shoring equipment is inspected before erection and damaged or weakened equipment is not used unless reinforced as required. |
| Adjustment | Install and adjust to the drawings; do not raise formwork by adjusting single-post shores after concrete placement. |
| Removal sequence | Leave reshores in place until supported concrete can carry its own weight and all loads placed on it. |
What a reshore does
Original shores support the formwork during placement and early curing. Reshores are installed as the original forms and shores are removed so partially cured concrete can continue to support construction loads. That load may include the concrete above, workers, equipment, materials, and forces from later placements.
The load does not disappear when an original shore is removed. It moves through the slab and the remaining support system. A reshore that is misplaced, poorly seated, or installed at the wrong stage can change how that load travels and overload concrete that has not gained enough strength.
“Tight” means firm contact, not lifting the slab
OSHA requires shore heads, base plates, extension devices, and adjustment screws to be in firm contact with the form and foundation, and secured when necessary. That is a contact and stability requirement. It is not permission to jack the slab upward or preload a shore beyond the formwork plan.
Follow the designer’s sequence and adjustment details. Do not improvise by forcing a reshore into place, lifting a slab, or tightening one support in a way that redistributes load to other supports. If the detail does not show the required fit or the field condition differs from the drawing, stop and get direction from the responsible designer or supervisor.
Inspection and damage checks
Inspect shoring equipment before erection to confirm it matches the formwork drawings. Inspect erected shores immediately before, during, and immediately after concrete placement. If equipment is damaged or weakened below the required capacity, it must be reinforced; equipment that is already too weak must not be used.
Check the sill and bearing surface as carefully as the post. A strong post on a soft, unstable, or undersized base does not create a safe support. Look for settlement, loose contact, eccentric loading, displacement, damaged threads, bent members, and missing bracing.
When reshoring is required and when it can come out
Reshoring is required as the original forms and shores are removed whenever the concrete would otherwise have to carry loads beyond its capacity. The decision depends on construction sequence, concrete strength, loads, spans, and the design. A calendar estimate alone does not establish that the slab can carry the load.
Reshores stay until the supported concrete has adequate strength for its self-weight and every load in place. OSHA permits the determination to follow the plans and specifications when their removal conditions are met, or appropriate concrete testing that shows sufficient compressive strength. Removing a reshore early can transfer the full load to a weaker slab.
If a reshore will not seat as shown, do not force, extend, or relocate it by guesswork. Verify the drawing and get an approved direction before changing the load path.
A practical review before installation
- Confirm the latest formwork and reshoring drawings are available.
- Check that the proposed sequence matches the plan and the slab’s current strength.
- Inspect the shore, base, head, adjustment hardware, bracing, and bearing surface.
- Set the member at the shown location and make the specified bearing points firm and secure.
- Check alignment and loading; do not use eccentric loading unless the member was designed for it.
- Inspect during placement and correct unsafe movement or damage promptly.
- Keep reshores in place until the removal criteria are satisfied.
For exam questions, distinguish the design requirement from a field guess. The safe answer is that reshores follow the formwork drawings, maintain intended firm contact, and remain until the concrete can safely carry the loads. No single turns-of-the-screw rule applies to every shore system.
Common questions
How tight should a reshore be?
Set it to the formwork drawings so the specified bearing surfaces are in firm contact. Do not use adjustment to jack the slab or create a load the design did not intend.
When are reshores required?
They are required as original forms and shores are removed whenever the concrete must be supported to prevent loads from exceeding its capacity.
Can shores be tightened after concrete has been placed?
OSHA prohibits adjusting single-post shores after concrete placement to raise the formwork. Follow the approved plan and get design direction rather than trying to lift or preload the slab.
When can a reshore be removed?
Only when the concrete it supports has adequate strength for its own weight and all loads in place, as established under the applicable plans or appropriate strength testing.